Cloth+RigidBody limitation #82817

New Issue

Andrea Coppola · 2020-11-18T16:30:53+01:00

Andrea Coppola commented

2020-11-18 16:30:53 +01:00

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce RTX 2080 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 457.30

Blender Version
Broken: version: 2.90.1, branch: master, commit date: 2020-09-23 06:43, hash: 3e85bb34d0
Worked: (newest version of Blender that worked as expected)

Short description of error
Hi,
I wonder that to make interactive a rigid body and a cloth (so that cloth can be deformed by the rigid body after collision), I had to create a phantom-collider parented with the rigid body to whom I applied a Collision. This is the only method to have interactivity between the 2 object.
I noticed that making the same execise in Blender 2.79, the rigid body naturally defermed the cloth, without the phantom-collider parented.
Why?

Exact steps for others to reproduce the error
#82817.blend

Open file
Play animation
Cloth should collide with Sphere, but it doesn't

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits Graphics card: GeForce RTX 2080 SUPER/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 457.30 **Blender Version** Broken: version: 2.90.1, branch: master, commit date: 2020-09-23 06:43, hash: `3e85bb34d0` Worked: (newest version of Blender that worked as expected) **Short description of error** Hi, I wonder that to make interactive a rigid body and a cloth (so that cloth can be deformed by the rigid body after collision), I had to create a phantom-collider parented with the rigid body to whom I applied a Collision. This is the only method to have interactivity between the 2 object. I noticed that making the same execise in Blender 2.79, the rigid body naturally defermed the cloth, without the phantom-collider parented. Why? **Exact steps for others to reproduce the error** [#82817.blend](https://archive.blender.org/developer/F9360944/T82817.blend) - Open file - Play animation Cloth should collide with Sphere, but it doesn't

Andrea Coppola commented

2020-11-18 16:30:53 +01:00

Added subscriber: @blenderhighschool

blender-admin commented

2020-11-18 16:30:53 +01:00

#83594 was marked as duplicate of this issue

blender-admin commented

2020-11-18 16:30:53 +01:00

#83679 was marked as duplicate of this issue

Richard Antalik commented

2020-11-23 20:32:05 +01:00

Added subscriber: @iss

Richard Antalik commented

2020-11-23 20:32:05 +01:00

I think this should work, though your file does have dependency cycles, which often cause simulations to misbehave. Check Window > Toggle System Console.

I will replace example file

I think this should work, though your file does have dependency cycles, which often cause simulations to misbehave. Check Window > Toggle System Console. I will replace example file

Richard Antalik commented

2020-11-23 20:34:29 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Andrea Coppola commented

2020-11-24 07:39:58 +01:00

Yes it works, but it doesn't seem like a normal workflow to me. Why did it work automatically in version 2.79 and from 2.8 onwards you have to find these absurd tricks?

Jacques Lucke commented

2021-01-06 13:51:17 +01:00

Added subscriber: @JacquesLucke

Jacques Lucke commented

2021-01-06 13:51:17 +01:00

Usually, if you want to compare behavior in 2.7x and 2.9x, it would be helpful to provide either a test file that works in both versions, or one .blend file for each version.

In any case, the main issue here is that Blenders physics system is just not capable of handling these kinds of interactions reliably yet. The fact that it worked in an older version was probably more "by accident". The new depsgraph "disabled" some functionality that kind of worked in the past, but weren't designed to work correctly.
To get similar behavior in the new depsgraph, you have to use tricks as you noticed. This is unfortunate, but it is unlikely that this will change before we improve our physics system in general (we might start to work on it this year).

Until then, this is a known issue. Thanks for the report anyway.

Usually, if you want to compare behavior in 2.7x and 2.9x, it would be helpful to provide either a test file that works in both versions, or one .blend file for each version. In any case, the main issue here is that Blenders physics system is just not capable of handling these kinds of interactions reliably yet. The fact that it worked in an older version was probably more "by accident". The new depsgraph "disabled" some functionality that kind of worked in the past, but weren't designed to work correctly. To get similar behavior in the new depsgraph, you have to use tricks as you noticed. This is unfortunate, but it is unlikely that this will change before we improve our physics system in general (we might start to work on it this year). Until then, this is a known issue. Thanks for the report anyway.

Jacques Lucke commented

2021-01-06 14:03:44 +01:00

Added subscribers: @TobiaszunfaKaron, @Fernando-Alcala, @jwvdronkelaar

Fernando Alcala commented

2021-01-07 01:14:15 +01:00

I found the issue. Collision sources Final and Deform don't work (as expected) but Base does.
the most based convex hull.mp4

I found the issue. Collision sources *Final* and *Deform* don't work (as expected) but *Base* does. [the most based convex hull.mp4](https://archive.blender.org/developer/F9553627/the_most_based_convex_hull.mp4)

Luis F. Carranza commented

2021-05-12 19:21:08 +02:00

Added subscriber: @Mpc46

Luis F. Carranza commented

2021-05-12 19:21:08 +02:00

Hopefully is gonna get fixed soon 🌮

Andrea Coppola commented

2021-05-12 19:57:39 +02:00

Thanx

Philipp Oeser removed the

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Cloth+RigidBody limitation #82817